# Half-Life Inquiry **URL:** \ **Category:** Factual Questions\ **Created:** [July 9, 2025, 4:25pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665 "2025-07-09T16:25:36Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![IridiumIodineSulfur](https://avatars.discourse-cdn.com/v4/letter/i/b9e5f3/32.png) [@IridiumIodineSulfur](https://boards.straightdope.com/u/IridiumIodineSulfur)\ **Post date:** [July 14, 2025, 2:12am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/21 "2025-07-14T02:12:26Z")
I meant immediately, as in when you open the box or however you start looking. ---
**Author:** ![IridiumIodineSulfur](https://avatars.discourse-cdn.com/v4/letter/i/b9e5f3/32.png) [@IridiumIodineSulfur](https://boards.straightdope.com/u/IridiumIodineSulfur)\ **Post date:** [September 17, 2025, 2:00am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/22 "2025-09-17T02:00:52Z")
I believe it is similar to the two slit experiment: the electron is in a superposition of going through the left hole and the right hole. ---
**Author:** ![IridiumIodineSulfur](https://avatars.discourse-cdn.com/v4/letter/i/b9e5f3/32.png) [@IridiumIodineSulfur](https://boards.straightdope.com/u/IridiumIodineSulfur)\ **Post date:** [September 17, 2025, 2:03am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/23 "2025-09-17T02:03:46Z")
I didn’t know that, that’s neat! I meant that once you open the box, you can’t see it. If you open a box with a cat, you can probably accurately say if the cat is dead or alive immediately. ---
**Author:** ![IridiumIodineSulfur](https://avatars.discourse-cdn.com/v4/letter/i/b9e5f3/32.png) [@IridiumIodineSulfur](https://boards.straightdope.com/u/IridiumIodineSulfur)\ **Post date:** [September 17, 2025, 2:06am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/24 "2025-09-17T02:06:57Z")
If I’m not mistaken, Schrödinger’s Cat only applies to the Copenhagen. In the Many Worlds, they wouldn’t say the cat is both alive and dead, but rather the cat being put in the box split into two worlds. Correct me if I’m wrong. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [September 17, 2025, 12:56pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/25 "2025-09-17T12:56:16Z")
Whereas Heisenberg’s cat, if it’s not there, is just a blur. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [September 17, 2025, 6:14pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/26 "2025-09-17T18:14:41Z")
That is just the same thing in different words. In all these interpretations, being in **both** state A and B, or having **worlds** A and B, means the state is a linear combination of those other states. The “many-worlds” point of view, in particular, is that there is no weird “collapse” if you take into account the system as well as its environment. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [September 17, 2025, 7:04pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/27 "2025-09-17T19:04:38Z")
And yet we _perceive_ collapse; that is, the universe is not an infinite superposition of every possible wave function since the Big Bang. Or put another way, what makes the many worlds separate? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 17, 2025, 8:57pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/28 "2025-09-17T20:57:30Z")
The me in this world perceives this world. The me in some other world perceives that other world. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [September 17, 2025, 9:05pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/29 "2025-09-17T21:05:56Z")
But you just said “this world” and “some other world”; what makes the worlds separate? Even if collapse doesn’t invalidate every possible world save one, it apparently is making them separate. So _something_ is happening. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 17, 2025, 9:16pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/30 "2025-09-17T21:16:00Z")
What makes them separate is that different things happen in them. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [September 17, 2025, 10:09pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/31 "2025-09-17T22:09:20Z")
You’re still presupposing they’re separate. The whole point of superposition is that **everything** happens; where does the supposition “in different worlds” get tacked on? Because we don’t perceive reality as one giant wave function of everything that could have happened since the Big Bang, obviously; but _why_ is that so? ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [September 18, 2025, 9:39am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/32 "2025-09-18T09:39:12Z")
> [@Chronos](#): > > What makes them separate is that different things happen in them. Cf. experiments where a single photon (or whatever) literally takes a combination of paths, for example in the Elitzur–Vaidman Bomb Detector. The point is that there are some genuine quantum effects going on that cannot be explained by classical “worlds” that are utterly “separate”— yes, different things happen in them, but they _all_ happen, therefore a particle is able to interfere with itself and so forth. But the fact that you perceive certain results (even under the many-worlds interpretation) is due to some sort of quantum decoherence so that one “you” perceives A and and other B— not some weird mixture— even though both can happen. E.g., there was a recent thread in which it was explained why you cannot observe a radioactive atom that simultaneously decayed and did not decay: [Half-Life Inquiry - #20 by Pasta](https://boards.straightdope.com/t/half-life-inquiry/1020665/20) The amplitude of the weird mixtures are going to pretty instantly decay over time. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 18, 2025, 10:55am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/33 "2025-09-18T10:55:19Z")
> [@DPRK](#): > > E.g., there was a recent thread in which it was explained why you cannot observe a radioactive atom that simultaneously decayed and did not decay: [Half-Life Inquiry - #20 by Pasta](https://boards.straightdope.com/t/half-life-inquiry/1020665/20) That thread is in a superposition of “recent” and “current”. ---
**Author:** ![Frodo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/frodo/32/302_2.png) [@Frodo](https://boards.straightdope.com/u/Frodo)\ **Post date:** [September 18, 2025, 1:12pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/34 "2025-09-18T13:12:23Z")
Warning: clicking on that link could lead to a stack overflow error. ---
**Author:** ![Ancient\_Nerd](https://avatars.discourse-cdn.com/v4/letter/a/ed655f/32.png) [@Ancient\_Nerd](https://boards.straightdope.com/u/Ancient_Nerd)\ **Post date:** [October 7, 2025, 5:49am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/35 "2025-10-07T05:49:47Z")
> [@IridiumIodineSulfur](#): > > How do half-lives allow full decay? > > My understanding is that in time _t_, half of the radioactive sample decays. I don’t understand how the full sample can decay if it is a half of the sample at a time. Eventually, there will be one radioactive atom left. There cannot be half of the atom, and I know it doesn’t just stay there (then we’d have Oganesson), so what happens to the final atom? Back to the OP. Half life is actually a statistical concept. If you are down to one atom, you no longer have a statistically significant number of them. There is no way to be sure exactly how long it will last. You can say that after ten more half-lives, there is a 99.9% probability that it will be gone. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [October 7, 2025, 6:01pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/36 "2025-10-07T18:01:47Z")
The Many Worlds interpretation answered the why as “because it can’t be otherwise.” Every quantum possibility _must_ exist and create a separate universe, no matter how ridiculously many there are. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [October 7, 2025, 8:03pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/37 "2025-10-07T20:03:19Z")
I still don’t see where “and create a separate universe” comes from. The difference between the Copenhagen interpretation and Many Worlds is that the former presupposes that wave function collapse produces one single outcome and all the rest get tossed, while the latter says that all outcomes happen somewhere. Nonetheless, _something_ is happening at that point, some sort of splitting; reality isn’t one giant superposition of all possible values of the wavefunction of the universe. The only reason we suppose that there must be separate universes is because our minds rebel at the alternative: a formless chaos of everything and nothing existing simultaneously. But the question is, what’s preventing that? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 7, 2025, 9:16pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/38 "2025-10-07T21:16:13Z")
The Many Worlds interpretation is one giant superposition of all possible values of the wavefunction of the Universe. It just doesn’t look like that to us, because we ourselves are among the things being superposed. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [October 8, 2025, 2:08am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/39 "2025-10-08T02:08:23Z")
And yet we don’t observe cats being alive and dead at the same time. Even photons and electrons are when observed localized, although the probability of seeing them where we find them is innately dependent on that unseen superposition. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [October 8, 2025, 3:22am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/40 "2025-10-08T03:22:16Z")
> [@Lumpy](#): > > reality isn’t one giant superposition of all possible values of the wavefunction of the universe Math is the issue. As I understand it, all the accepted interpretations of QM are mathematically equivalent. Therefore if one is wrong then they are all wrong. No proof has yet been forthcoming that QM is wrong, so the Many Worlds interpretation will stay until that happens. Physicists can decide which interpretation they prefer and many - the shut up and calculate group, which is probably the majority - don’t care at all. Your assertion about the reality of the universe is a bold claim. However, without your providing the math behind that statement there’s not much that anybody can do with it. (Well, except refute it as Chronos has. I’m not stepping into it.) [Previous page](https://boards.straightdope.com/t/half-life-inquiry/1020665.md?page=1) [Next page](https://boards.straightdope.com/t/half-life-inquiry/1020665.md?page=3)